The dialkyl carbonate is utilized in industry to prepare pharmaceutically active compounds, agricultural chemicals, urethane, and polycarbonate or is as such utilized as a solvent.
U.S. Pat. No. 4,544,507 discloses that the dialkyl carbonate can be prepared by heating a dialkyl oxalate in a liquid phase at a temperature of 50 to 150.degree. C. in the presence of an alcoholate catalyst, by which the dialkyl oxalate is decarbonylated. This preparation process in the liquid phase has disadvantageous features in that separation and recovery of the produced dialkyl carbonate and the catalyst from the reaction mixture require complicated procedures. Moreover, this process is not satisfactory from the viewpoint of industrial production, because the yield of the target dialkyl carbonate is low and further the selectivity to the target dialkyl carbonate is low due to accompanying side-reactions which give various by-products.